Middlesbrough manager Gareth Southgate has confirmed that Robert Huth has suffered a fresh ankle injury.
Huth has suffered an injury-plagued time on Teesside since his £6million move from Chelsea in 2006.
The Germany international has been limited to just 23 league starts, but he looked to have put his problems behind him this season after starting the first six games with no problems.
But now Huth has damaged ankle ligaments, which will be a huge concern for Boro given he had to undergo ankle surgery last year.
"Robert has a problem with his ankle ligaments but we don't yet know the full extent of the injury," said Southgate.
"The area is very swollen and it's difficult to give an accurate assessment at this stage.
"However we should have a clearer picture by the end of the week."
With Emanuel Pogatetz suspended and youngster Rhys Williams already sidelined, Boro are left with few options other than Chris Riggott and David Wheater in central defence.
Jonathan Grounds, who was recalled from a loan spell at Norwich, can also play in the middle, but with Andrew Taylor also set for a time on the sidelines with a hip injury, he is needed at left-back.
Southgate is now keeping his fingers crossed that his international players return unscathed - last time round both Tuncay Sanli and Mohamed Shawky picked up injuries with their countries.
He added: "The international break wasn't too kind to us last time.
"We've got a lot of players away again this week. In fact we've got only six or seven left.
"Hopefully everybody will come back fine this time. After the win against Wigan, everybody will want to play against Chelsea."
Southgate confirmed that Tuncay could be back for the next Premier League clash with Luiz Felipe Scolari's leaders after his knee problem.
"The Chelsea game is one of Tuncay's targets but he will not be considered unless he is fully fit," he said.
"I can't say yet when he will be ready to start, but he should be very close by the end of next week. The week after is a more realistic target but we'll have to see."